Malaria epidemiology and demographics: Difference between revisions

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'''For patient information click [[Malaria (patient information)|here]]'''


{{CMG}}
{{Malaria}}
==Distribution and impact==
{{further|[[Diseases of poverty]], [[Tropical disease]]}}
[[Image:Malariageodistribution.png|350px|thumb|Areas of the world where malaria is [[Endemic (epidemiology)|endemic]] in the 21st Century (coloured blue).<ref>{{cite web | title = Malaria: Geographic Distribution | work = CDC Malaria website | url = http://www.cdc.gov/malaria/distribution_epi/distribution.htm | accessdate = 2007-06-15}}</ref>]]
Malaria causes about 400&ndash;900 million cases of fever and approximately one to three million deaths annually <ref name=Breman>{{cite journal | author = Breman J | title = The ears of the hippopotamus: manifestations, determinants, and estimates of the malaria burden. | url=http://www.ajtmh.org/cgi/reprint/64/1_suppl/1-c | journal = Am J Trop Med Hyg | year=2001 | volume = 64 | issue = 1-2 Suppl | pages = 1-11 | year = 2001 | pmid = 11425172}}</ref> &mdash; this represents at least one death every 30 seconds.  The vast majority of cases occur in children under the age of 5 years;<ref name="greenwood2005">{{cite journal | author=Greenwood BM, Bojang K, Whitty CJ, Targett GA | title=Malaria | journal=Lancet | year=2005 | volume=365 | pages=1487-1498  | pmid = 15850634}}</ref> pregnant women are also especially vulnerable. Despite efforts to reduce transmission and increase treatment, there has been little change in which areas are at risk of this disease since 1992.<ref>{{cite journal | author = Hay S, Guerra C, Tatem A, Noor A, Snow R | title = The global distribution and population at risk of malaria: past, present, and future. | journal = Lancet Infect Dis | volume = 4 | issue = 6 | pages = 327-36 | year = 2004 | pmid = 15172341}}</ref> Indeed, if the prevalence of malaria stays on its present upwards course, the death rate could double in the next twenty years.<ref name=Breman/> Precise statistics are unknown because many cases occur in rural areas where people do not have access to hospitals or the means to afford health care. Consequently, the majority of cases are undocumented.<ref name=Breman/>
Although co-infection with HIV and malaria does cause increased mortality, this is less of a problem than with HIV/[[tuberculosis]] co-infection, due to the two diseases usually attacking different age-ranges, with malaria being most common in the young and active tuberculosis most common in the old.<ref>{{cite journal | author = Korenromp E, Williams B, de Vlas S, Gouws E, Gilks C, Ghys P, Nahlen B | title = Malaria attributable to the HIV-1 epidemic, sub-Saharan Africa. | url=http://www.cdc.gov/ncidod/EID/vol11no09/05-0337.htm | journal = Emerg Infect Dis | volume = 11 | issue = 9 | pages = 1410-9 | year = 2005 | pmid = 16229771}}</ref> Although HIV/malaria co-infection produces less severe symptoms than the interaction between HIV and TB, HIV and malaria do contribute to each other's spread. This effect comes from malaria increasing [[viral load]] and HIV infection increasing a person's susceptibility to malaria infection.<ref>{{cite journal |author=Abu-Raddad L, Patnaik P, Kublin J |title=Dual infection with HIV and malaria fuels the spread of both diseases in sub-Saharan Africa |journal=Science |volume=314 |issue=5805 |pages=1603-6 |year=2006 | pmid = 17158329}}</ref>
Malaria is presently endemic in a broad band around the equator, in areas of the Americas, many parts of Asia, and much of Africa; however, it is in sub-Saharan Africa where 85&ndash; 90% of malaria fatalities occur.<ref>{{cite web | author = Layne SP | title = Principles of Infectious Disease Epidemiology /| work =  EPI 220 | publisher = UCLA Department of Epidemiology | url = http://web.archive.org/web/20060220083223/http://www.ph.ucla.edu/epi/layne/Epidemiology+220/07.malaria.pdf | accessdate = 2007-06-15}}</ref> The geographic distribution of malaria within large regions is complex, and malarial and malaria-free areas are often found close to each other.<ref name="greenwood2002">{{cite journal | author=Greenwood B, Mutabingwa T | title=Malaria in 2002 | journal=Nature | year=2002 | volume=415 | pages=670–2  | pmid = 11832954}}</ref> In drier areas, outbreaks of malaria can be predicted with reasonable accuracy by mapping rainfall.<ref>{{cite journal | author = Grover-Kopec E, Kawano M, Klaver R, Blumenthal B, Ceccato P, Connor S | title = An online operational rainfall-monitoring resource for epidemic malaria early warning systems in Africa. | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15663795 | journal = Malar J | volume = 4 | issue = | pages = 6 | year = 2005 | pmid = 15663795}}</ref> Malaria is more common in rural areas than in cities; this is in contrast to [[dengue fever]] where urban areas present the greater risk.<ref>{{cite journal |author=Van Benthem B, Vanwambeke S, Khantikul N, Burghoorn-Maas C, Panart K, Oskam L, Lambin E, Somboon P |title=Spatial patterns of and risk factors for seropositivity for dengue infection | url=http://www.ajtmh.org/cgi/content/full/72/2/201 |journal=Am J Trop Med Hyg |volume=72 |issue=2 |pages=201-8 |year=2005 | pmid = 15741558}}</ref> For example, the cities of the Vietnam, Laos and Cambodia are essentially malaria-free, but the disease is present in many rural regions.<ref>{{cite journal |author=Trung H, Van Bortel W, Sochantha T, Keokenchanh K, Quang N, Cong L, Coosemans M |title=Malaria transmission and major malaria vectors in different geographical areas of Southeast Asia |journal=Trop Med Int Health |volume=9 |issue=2 |pages=230-7 |year=2004 | pmid = 15040560}}</ref> By contrast, in Africa malaria is present in both rural and urban areas, though the risk is lower in the larger cities.<ref>{{cite journal |author=Keiser J, Utzinger J, Caldas de Castro M, Smith T, Tanner M, Singer B |title=Urbanization in sub-saharan Africa and implication for malaria control | url=http://www.ajtmh.org/cgi/content/full/71/2_suppl/118 |journal=Am J Trop Med Hyg |volume=71 |issue=2 Suppl |pages=118-27 |year=2004 |id=PMID 15331827}}</ref> The global [[Endemic (epidemiology)|endemic]] levels of malaria have not been mapped since the 1960s, however, the [[Wellcome Trust]], UK, has funded the [[Malaria Atlas Project]]<ref>{{cite journal | author = Hay SI, Snow RW | title = The Malaria Atlas Project: Developing Global Maps of Malaria Risk. | url = http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030473 | journal = PLoS Medicine | volume = 3 | issue = 12 | pages = e473 | year = 2006 }}</ref> to rectify this, providing a more contemporary and robust means with which to assess current and future malaria [[disease burden]].
===Socio-economic effects===
Malaria is not just a disease commonly associated with poverty, but is also a cause of poverty and a major hindrance to economic development. The disease has been associated with major negative economic effects on regions where it is widespread. A comparison of average per capita GDP in 1995, adjusted to give parity of purchasing power, between malarious and non-malarious countries demonstrates a fivefold difference (US$1,526 versus US$8,268).  Moreover, in countries where malaria is common, average per capita GDP has risen (between 1965 and 1990) only 0.4% per year, compared to 2.4% per year in other countries.<ref name="sachs2002">{{cite journal | author=Sachs J, Malaney P | title=The economic and social burden of malaria | journal=Nature | year=2002 | volume=415 | pages=680-5 | pmid = 11832956}}</ref> However, correlation does not imply causation, and the prevalence is at least partly because these regions do not have the financial capacities to prevent malaria. In its entirety, the economic impact of malaria has been estimated to cost Africa US$12 billion every year.  The economic impact includes costs of health care, working days lost due to sickness, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism.<ref name="greenwood2005"/>  In some countries with a heavy malaria burden, the disease may account for as much as 40% of public health expenditure, 30-50% of inpatient admissions, and up to 50% of outpatient visits.<ref>{{cite web | author=Roll Back Malaria | title=Economic costs of malaria | url=http://www.rbm.who.int/cmc_upload/0/000/015/363/RBMInfosheet_10.htm|publisher=[[World Health Organization|WHO]] | accessdate=2006-09-21}}</ref>
==References==
{{reflist|3}}

Revision as of 14:50, 12 June 2012